JPH0719089A - Engine stability control device - Google Patents

Abstract

(57) [Summary] [Purpose] The feedback correction amount is prohibited from being updated when the auxiliary load changes suddenly, so that it is not affected by the rotational fluctuation caused by the rapid change in the auxiliary load. [Structure] The calculation unit 52 calculates the stability of combustion from the engine speed fluctuation, and the updating unit 53 updates the feedback correction amount so that the detected value of the stability falls within an allowable level. The calculation unit 54 calculates the correction amount of the basic control amount based on this feedback correction amount, and the calculation unit 54 corrects the basic control amount from the basic control amount calculation unit 51 with this correction amount to control the control amount of the engine control factor. To calculate. The control means 56 controls the engine control factor with this control amount.
When the determining means 57 determines that there is a sudden change in the auxiliary machine load, the inhibiting means 58 inhibits the updating of the feedback correction amount.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine stability control device, and more particularly to an engine stability control device that calculates combustion stability from fluctuations in engine rotation to optimally control engine control factors.

[0002]

2. Description of the Related Art Differences in fuel affect engine control factors such as engine air-fuel ratio and ignition timing. Therefore, factors that change depending on fuel properties (mainly fuel volatility) and fuel properties are detected. In some cases, it is determined from the detection result whether the volatility of the fuel is good or bad, and the determination result is reflected in the engine control factor to improve the stability of the engine or the emission at the time of transition.

To explain this, in Japanese Patent Laid-Open No. 2-5744, it is judged whether the gasoline is heavy gasoline or heavy gasoline (which has lower volatility than ordinary gasoline) based on the fluctuation range of rotation at idle, and the air-fuel ratio is determined based on the result. And switch the ignition timing control map. Further, in Japanese Patent Laid-Open No. 63-272935, general gasoline is a heavy gasoline due to the size of the difference between the actual air-fuel ratio and the target air-fuel ratio at the time of transition, the presence or absence of backfire, and the length of complete explosion time at low temperature start. I'm making a decision. As disclosed in Japanese Patent Laid-Open No. 62-228139, there is a method in which the fuel property is judged from the combustion light detected by an optical sensor, the degree of response delay of the air-fuel ratio during acceleration, and the magnitude of torque generated during acceleration.

[0004]

By the way, in the above apparatus, heavy gasoline is used for the control characteristics matching with general gasoline, and it is determined that the fuel used is heavy gasoline due to unstable combustion. Until then, the instability of combustion is not reflected in the engine control factor, and combustion is left unstable, and during that time, drivability may deteriorate.

Further, if the combustion becomes unstable even once due to the mismatch between the engine control characteristics and the used fuel, there is a phenomenon (hysteresis) that the degree of instability of the combustion further advances. The accuracy is not good.
In a region where rotation fluctuation occurs due to deterioration of combustion, large engine variations (variations in residual gas and ignition energy, differences in intake air temperature and humidity, etc.) also lead to deterioration in detection accuracy. In other words, it becomes impossible to distinguish between the deterioration of combustion caused by factors other than the fuel property and the deterioration of combustion due to deterioration of the volatility of the fuel. On the other hand, if the sensor for directly detecting the fuel property of heavy gasoline and the above-mentioned optical sensor for indirectly detecting the fuel property are newly provided, an increase in cost cannot be avoided.

Therefore, the combustion stability is calculated from the engine speed fluctuation, and the air-fuel ratio during warm-up, which has a strong correlation with the combustion stability, is feedback-corrected so that the combustion stability falls within an allowable level. At the same time, the feedback correction amount is used as the fuel property signal, so that there is no need to newly provide a sensor for detecting the fuel property, and even when heavy gasoline is used, the air-fuel ratio during warm-up is not lean. , It became possible to prevent the deterioration of stability in idling due to insufficient warm-up increase.

However, in this device, even if the combustion is stable, if the rotation fluctuation occurs due to a sudden change in the auxiliary load such as a factor other than the fuel property, that is, switching of the auxiliary load, the combustion will not be completed. Since the air-fuel ratio is erroneously controlled to become rich as it becomes stable, fuel consumption becomes worse and H
Emissions of C and CO increase.

For example, an air conditioner compressor is connected to and disengaged from a crankshaft by an electromagnetic clutch attached to the air conditioner compressor. When the air conditioner switch is switched from OFF to ON, the air conditioner compressor is driven by the engine and the switch is activated. When you turn off the
The load on the air conditioner compressor is released from the engine. Immediately after this switching of the compressor load, the engine speed temporarily fluctuates as shown in FIG. 26, and a feedback correction amount (a stabilized fuel-air ratio correction coefficient Lldml described later) is irrelevant regardless of instability of combustion. ) Is updated to the larger side as indicated by the broken line, and the air-fuel ratio during warm-up is erroneously controlled to the rich side.

Therefore, an object of the present invention is to prevent the influence of the rotation fluctuation caused by the sudden change of the auxiliary machine load by prohibiting the update of the feedback correction amount when the auxiliary machine load suddenly changes.

[0010]

As shown in FIG. 1, a first invention is a means 51 for calculating a basic control amount of an engine control factor from an engine operating condition signal, and a combustion stabilization based on a fluctuation in engine rotation. Degree, a means 53 for updating the feedback correction amount so that the detected value of the stability falls within an allowable level, and a means 54 for calculating the correction amount of the basic control amount based on the feedback correction amount. A means 55 for calculating the control amount of the engine control factor by correcting the basic control amount with this correction amount, a means 56 for controlling the engine control factor with this control amount, and a sudden change of the auxiliary machine load. A means 57 for determining whether or not there is provided, and a means 58 for prohibiting the update of the feedback correction amount when the auxiliary load suddenly changes based on the result of this determination are provided.

According to a second aspect of the present invention, the prohibition of updating the feedback correction amount is from when the auxiliary load suddenly changes to after a predetermined period.

[0012]

[Function] When the auxiliary load suddenly changes, rotational fluctuations unrelated to the unstable combustion occur. Therefore, even when the load suddenly changes, if the feedback correction amount is updated so that the combustion stability is within the allowable level, the engine control Factors are erroneously controlled on the side that stabilizes combustion.

On the other hand, according to the first aspect of the present invention, the update of the feedback correction amount is prohibited when the load suddenly changes, so that the feedback correction amount does not change immediately after the sudden change in the auxiliary machine load.
Erroneous control can be avoided.

In the second aspect of the present invention, if the updating is prohibited from the time when the auxiliary load changes abruptly until after a predetermined period, erroneous control to the side that stabilizes combustion can be reliably prevented.

[0015]

In FIG. 2, fuel is injected from a single injector 4 provided in the intake port regardless of whether the amount is large or small. Therefore, the amount of fuel is adjusted by the control unit 21 according to the injection time. . The injection amount increases as the injection time increases, and the injection amount decreases as the injection time decreases. The richness of the air-fuel mixture, that is, the air-fuel ratio, shifts to the rich side when the fuel injection amount for a fixed amount of intake air increases,
If the fuel injection amount decreases, it shifts to the lean side.

Therefore, if the basic injection amount of fuel is determined so that the ratio to the intake air amount becomes a constant value, the same air-fuel ratio can be obtained even under different operating conditions. When the fuel injection is performed once per one revolution of the engine, the basic injection pulse width Tp is calculated from the intake air amount at that time and the engine speed with respect to the air amount sucked in one revolution.
Usually, the air-fuel ratio determined by this Tp is near the stoichiometric air-fuel ratio.

By the way, when heavy gasoline is used when the control characteristics of the engine are determined for the normal gasoline, the volatility of the fuel of the heavy gasoline is worse than that of the normal gasoline, so that the combustion state is particularly bad. Drivability is greatly affected by operating conditions. During warm-up immediately after startup, where the combustion is not stable, the water temperature increase correction coefficient Ktw and the post-start increase correction coefficient Ka are tried to operate at an air-fuel ratio that is richer than the theoretical air-fuel ratio.
The fuel quantity increase is corrected using s and
When these increasing factors are matched with general gasoline, the use of heavy gasoline deteriorates combustion due to the deterioration of fuel volatility.

In order to deal with this, the control unit 21 calculates the combustion stability from the engine speed fluctuation, and a feedback correction amount (a stabilized fuel-air ratio which will be described later) so that the combustion stability falls within an allowable level. Correction coefficient Ll
dml), the air-fuel ratio correction amount is calculated based on this feedback correction amount, and the air-fuel ratio during warm-up is corrected with this correction amount, the combustion stability and fuel volatility are limited only during warm-up. Since the fuel used is a heavy gasoline and the calculated stability calculation value is out of the allowable range, it is again within the allowable level. The difference with the air-fuel ratio correction amount when the calculated value of is within the allowable level accurately corresponds to the difference in volatility between heavy gasoline and general gasoline.

In this case, if the air-fuel ratio correction amount is set to zero when using general gasoline, the air-fuel ratio correction amount has a non-zero value when using heavy gasoline, and this non-zero The fuel ratio correction amount becomes a signal representing the difference from the volatility of general gasoline.

Furthermore, since the difference from the volatility of general gasoline is almost the same as the decrease in temperature, the above air-fuel ratio correction amount can be converted into a temperature correction amount. For example, the value obtained by subtracting the air-fuel ratio correction amount from the cooling water temperature Tw is set again as the water temperature correction temperature Twl, and the water temperature increase correction coefficient and the post-start increase amount are referenced by referring to the table set for this gasoline temperature correction temperature Twl. If the correction coefficient is calculated, a larger injection amount is supplied than when using general gasoline, and even when using heavy gasoline, combustion during warm-up can be stabilized in the same manner as general gasoline.

However, even if the combustion is stable, if the rotation of the auxiliary load changes due to a sudden change of the auxiliary load or the like, the combustion becomes unstable and the air-fuel ratio is erroneously controlled to the rich side. As a result, fuel consumption becomes worse and H
Emissions of C and CO increase.

In order to cope with this, the control unit 21 prohibits the update of the feedback correction amount when the auxiliary load changes suddenly.

Therefore, the signal from the air conditioner switch 32, the power steering switch 34, etc. (see FIG. 25) is the signal from the sensor (7 is sucked from the air cleaner) necessary for the stability control during the warm-up. Air volume Q
An air flow meter for detecting a, 9 is an idle switch, 10 is a crank angle sensor for outputting a signal for each unit crank angle and a crank angle reference signal, and 11 is a water temperature sensor), and is input to a control unit 21 including a microcomputer. ing. 12 is an O ₂ sensor, 13
Is a knock sensor, and 14 is a vehicle speed sensor.

[1] Calculation of Rotational Fluctuation Since rotational fluctuation occurs due to instability of combustion, the period between REFs (the period between reference signals REF) is measured, and this RE is measured.
The rotation speed for each cylinder is calculated based on the added value of the latest value and the previous value in the period between F, and the stability of combustion is estimated from the variation in the rotation speed for each cylinder.

In FIG. 4, the cycle Refrv of one engine revolution section is calculated from the cycle REF between REFs: Refrv = Ref + Ref _n-1 (1) where Ref _n-1 ; the previous cycle between REFs (FIG. 4) Step 11), Nerv = KN # / Refrv (2) where KN #; cycle-to-rotation speed conversion constant is converted to the cylinder-by-cylinder rotation speed Nerv (step 13 in FIG. 4).

The reason why the formula (1) is derived is as follows. 4-cylinder engine (ignition order # 1- # 3- # 4
FIG. 5 shows the relationship between the combustion pressure and the rotational fluctuation of each cylinder and the reference signal REF (which rises every 180 ° CA) for the (-# 2). Rotational fluctuations due to combustion in each cylinder occur according to the ignition sequence for each 180 ° CA (crank angle of engine half rotation), whereas the reference signal REF is a predetermined crank angle before compression top dead center (TDC in the figure). When rising at (for example, 110 ° CA), one combustion section and the REF cycle of the cylinder in which the combustion is performed are temporally displaced.

If the # 3 cylinder is used as a representative, the rotation fluctuation (from # 3TDC to # 4TDC) due to the combustion of the # 3 cylinder spans two cycles of the # 3REF cycle and the # 4REF cycle. The crank angle range in which the combustion of the cylinder contributes is 110 ° CA in the cycle between # 4REF (from the figure to # 4TDC) and 70 ° CA in the cycle between # 3REF (from # 3TDC). is there. Assuming that the contribution ratios are k ₁ and k ₂ , respectively, k ₁ = 110/180 (1.1) k ₂ = 70/180 (1.2), and the half rotation section cycle of the # 3 cylinder is # 3 cylinder half-rotation period cycle = # 4 REF inter-cycle × k ₁ + # 3 REF inter-cycle × k ₂ (1.3)

Here, since the REF period is obtained in the ignition order, if the latest value Ref of the REF period obtained this time in equation (1.3) is associated with the # 4 cylinder, the previous value Ref _{n- of the} REF period is set. _{If 1} corresponds to the # 3 cylinder, and if the # 4 cylinder is considered as the current cylinder (current cylinder), the # 3 cylinder is the previous cylinder (the cylinder one before in the ignition order from the current cylinder). .3) can be rewritten as the half-rotation section cycle of the front cylinder = Ref × k ₁ + Ref _n−1 × k ₂ (1.4).

The formula (1.4) is a formula considering the # 4 cylinder as the current cylinder, but the formula is the same as the formula (1.4) even if the # 2, # 1, and # 3 cylinders are the current cylinders.

The above-mentioned contribution ratios k ₁ and k ₂ are obtained when the combustion starts from TDC (compression top dead center) in each cylinder. Considering that the actual combustion starts before TDC, requires correction by the combustion start crank angle, this time in the above (1.1), (1.2) in place of the equation, k ₁ = (110- combustion start crank angle) / 180 ... (1.5) k ₂ = (70 + combustion start crank angle) / 180 (1.6) must be used. For example, assuming that the average value of the combustion start crank angle is 20 ° CA before the compression top dead center, k ₁ = (110-20) /180=0.5 (1.7) k ₂ = (70 + 20) / 180 = 0.5 ... (1.8) Therefore, the equation (1.4) becomes the half rotation section cycle of the previous cylinder = Ref × 0.5 + Ref _n−1 × 0.5 (1.9) .

In practice, it is difficult to know the ignition timing, so the ignition timing is adopted as a value equivalent to the above combustion start crank angle.

By doubling both sides of the equation (1.9), one revolution section cycle of the front cylinder = Ref + Ref _n-1 (1.10) This equation (1.10) is the equation (1). is there. That is,
Since Refrv in the equation (1) represents one revolution section cycle of the previous cylinder, the latest value (Ref) of the cycle between REFs is calculated by the equation (1).
By converting the added value of the previous value (Ref _n-1 ) into the rotational speed unit by the equation (2), the rotational speed for each cylinder can be obtained.

When the two REF cycles (current value and previous value of the REF cycle) are shown in FIG. 6 as measurement intervals, the measurement intervals are as shown in FIG. 6 between two cylinders adjacent in the ignition order. It shifts while overlapping the measurement section.
When the cylinder-by-cylinder rotational speed is obtained in this way, the rotational fluctuation due to the variation between the cylinders is not mistakenly recognized as the rotational fluctuation due to the unstable combustion.

According to the equation (1.9), k is obtained as a result.
₁ and k ₂ are equal (both are 0.5),
This is <a> In-line 4-cylinder engine <b> REF rises at 110 ° CA before compression top dead center <c> Combustion start crank angle is 20 ° CA before compression top dead center 3 Only when all of the two conditions are satisfied, if any one of these conditions is not satisfied, k ₁ ≠ k ₂ .

From the cylinder-by-cylinder rotational speed Nev in the above equation (2), Dnerv = Nev-Nevn _-4 (3) where Nevn _-4 ; the rotational variation Dnerv for each cylinder in the Nev equation four times before. Is calculated (Fig. 4
Step 15).

When the cylinder-by-cylinder rotational speed Nev in the equation (2) is, for example, that of the # 1 cylinder (previous cylinder), Nev
_n-1 (the value one time before) is for # 2 cylinder, Nev _n-2 (the value before two times) is for # 4 cylinder, and Nev _n-3 (the value before three times) is #
Since it has three cylinders, in order to obtain the rotation change amount for the # 1 cylinder, the value four times before (that is, the value one cycle before) must be used in the equation (3). As described above, by obtaining the difference between the latest value of the cylinder-by-cylinder rotational speed and the value one cycle before as the cylinder-by-cylinder rotational change amount Dnerv, the variation between the cylinders is not mistaken for rotational fluctuation due to unstable combustion. That is why.

Before the calculation of the expression (2), the old Nev is shifted (step 12 in FIG. 4). This is an operation of sequentially transferring the data of one rotation before to the RAM of two times before, the data of two rotations before three times, and the data three rotations before four times. The engine speed N, which will be described later, is stored because the cylinder-by-cylinder rotation speed is stored by the shift of the old Nev.
e = Ne = (Nev + Nev _n-1 + Nev _n-2 + Ner
It can be calculated as the average value of the engine speeds of all cylinders by the formula of v _n-3 ) / 4.

The shift of the old Dnerv is similar to the shift of the old Nrv (step 14 in FIG. 4).

From the cylinder-by-cylinder rotational change amount Dnerv, Llj = Dnerv-Dnerv _n-1 (4) where Dnerv _n-1 ; The amount is obtained as the torque fluctuation equivalent value Llj (step 16 in FIG. 4).

Since Dnerv in the equation (3) is the amount of change in rotation that has occurred between one revolution cycle during the previous combustion and one revolution cycle during the present combustion for a certain cylinder, Lner of the equation (4) is
Corresponds to a pseudo torque fluctuation amount due to combustion.

The torque fluctuation equivalent value Llj is bandpass filtered and the result is stored as a digital filtering output Lljd (steps 17 and 1 in FIG. 4).
8). Since the bandpass filter processing is performed by software, an equation converted from a continuous system to a discrete system is used. The frequency may be a frequency (3 to 7 Hz) that is easily felt by the driver of the vehicle as a surge.

[2] Condition for prohibiting update of feedback correction amount The operation condition for feedback correction of the air-fuel ratio (indicated by F / B in the figure) so that the stability of combustion falls within an allowable level is only during warm-up. So it's not a transition or a start. This is because combustion stability and fuel volatility have a strong correlation only during warm-up. On the other hand, when the required correction value determined by the volatility of the fuel used during the transition and the actual correction amount deviate, the deterioration of emission is a problem,
The difference in stability corresponding to the difference between the required value and the actual correction amount is not so large (the rotation fluctuation is large during the transition, and the stability may not be detected originally). Also, at the time of starting, it is a stage before combustion and has nothing to do with stability.

Specifically, as shown in FIG. 7, when any of the following conditions <1> to <10> is satisfied, the feedback correction inhibition flag is set to "1" to inhibit the feedback correction. (Step 33 in FIG. 7).

<1> The starting water temperature Tws is not within the predetermined range between the upper and lower limits (step 21 in FIG. 7). This prohibits feedback correction in extremely low temperature range where engine operation is impossible, high temperature range where combustion is unlikely to deteriorate,
This is because only a part of the water temperature region that is well adapted is used as the feedback correction region.

<2> Current water temperature Tw and starting water temperature Tws
Is greater than or equal to a predetermined value DTW # (step 22 in FIG. 7). If Tw-Tws ≥ DTW #, it is considered that it is in a stable region (a region in which the air-fuel ratio can be stably operated even if the air-fuel ratio slightly deviates from the stoichiometric air-fuel ratio and becomes lean) after starting, and feedback correction is prohibited. Is.

<3> The operating condition is not within the feedback correction area (step 23 in FIG. 7). As shown in FIG. 8, the entire operation region is divided into several regions by the rotation speed Ne and the cylinder air amount equivalent pulse width (engine load equivalent amount, which will be described later) Avtp, and the flag value is included therein. , Ne and Avtp, if the value referring to the map of FIG. 8 is “0”, the feedback correction is prohibited.
This is because the region of “0” is the high rotation speed region as shown in the figure, and combustion cannot deteriorate in the high rotation speed region.

<4> Gear position <predetermined value LLGR # (step 24 in FIG. 7). The higher the gear position, the greater the value assigned (eg 1
Feedback correction is prohibited when the gear position is <LLGR #, corresponding to the second speed, the third speed, the fourth speed, 1, 2, 3, 4).
This is because it is possible to prohibit the feedback correction (for example, the first speed is prohibited) because the rotation speed of the engine rapidly changes during low-speed gear running and causes disturbance to the stability. However, since feedback correction is desired during idling, correction is performed during idling even in the low gear position.

<5> The previous gear position and the current gear position are not the same (step 25 in FIG. 7). The reason why the feedback correction is prohibited when the gear position is changed is to prevent erroneous control due to the fact that the rotation change due to the gear change is regarded as the deterioration of the combustion.

<6> It is a transient time (steps 26, 27 and 28 in FIG. 7). The throttle valve opening Tvo, the cylinder air amount equivalent pulse width Avtp, and the amount of change of the engine speed Ne per predetermined time are at predetermined levels (LLDTVO # for the throttle valve opening, LLDTP # for the cylinder air amount equivalent pulse width, engine About rotation speed LLDNE
If it exceeds #), it is judged to be a transition and feedback correction is prohibited.

<7> The air conditioner switch (abbreviated as air conditioner Sw in the figure) is being switched (step 29 in FIG. 7).

In FIG. 25, when the air conditioner switch 32 is in the OFF state, since the relay 33 is turned off, current does not flow in the solenoid 31 for the electromagnetic clutch and the compressor does not work. However, when the air conditioner switch 32 is turned on, Since the relay 33 is closed and a current flows through the solenoid 31, the engine output is transmitted to the compressor via the electromagnetic clutch and the compressor is driven. When the air conditioner switch is turned off, the electromagnetic clutch is disengaged and the compressor load is removed from the engine. Rotational fluctuations occur due to switching of the compressor load accompanying the switching of the air conditioner switch, so feedback correction is prohibited in order to prevent erroneous control due to the fact that combustion fluctuations are considered to be deteriorated due to this rotational fluctuations.

<8> Switching of power steering switch (abbreviated as power steering Sw in the figure) (FIG. 7)
Step 30). This is because a change in the oil pump load that accompanies the change in the power steering switch causes a rotation fluctuation unrelated to the instability of combustion.

Specifically, in the oil pump for power steering, the discharge pressure increases and the driving torque increases by turning the handle. This is because the oil pump always rotates directly with the engine, but it has a servo mechanism as an actuator that just circulates the oil unless the handle is turned. The power steering switch 34 is a pressure switch which is turned on when the discharge pressure of the oil pump is a predetermined value (for example, several tens kg / cm ² ) or more.
It can be seen that the pump load is applied to the crankshaft by turning on 4 and the pump load is released from the crankshaft by turning off the power steering switch 34.

When the oil pump is electric, the power steering switch may be a pressure switch that is turned on when the motor load exceeds a predetermined value.

<9> The electric load switch (abbreviated as electric load Sw in the drawing) is being changed (step 31 in FIG. 7).

Here, the electric load is a combination of the ones that are turned on and off due to the large power consumption, and as shown in FIG. 25, for example, the power consumption is turned on and turned on and off.
Some of the electric loads to be flipped are selected (three of the heater fan motor 36, the light coil 39, and the rear defogger coil 42), and the respective auxiliary load switches (heater fan switch 37, light switch 4).
0, OR signal from rear defogger switch 43)
It is input to the control unit 21 via the circuit 45, and any one of the three switches 37, 40 and 43 is turned on.
When N, the electric load switch is turned on, the three switches 37,
The electrical load switch is OF when all 40 and 43 are OFF.
F (that is, the electric load switch is a generic name).

When the electric load switch is turned on, the motor 36
When a current flows through the coils 39 and 42 and the amount of power generated by the alternator directly connected to the engine increases, the driving torque of the alternator sharply increases (the alternator load changes abruptly), which causes fluctuations in rotation. .

O of the above lights, rear defogger, etc.
Since the power consumption at the time of N is known in advance, it can be assumed that the electric load switch is turned on when the combination of the switch ONs is estimated that the total power consumption exceeds a predetermined value.

When the heater fan switch has multiple stages, the number of stages to turn on the electric load switch may be appropriately determined according to the power consumption of each stage. As for the light, it can be appropriately determined which lighting is used to turn on the light switch 37 according to the power consumption in each lighting state of the small lamp, the low beam lamp, and the high beam lamp.

<10> When all of the above items <3> to <9> are not satisfied, the elapsed time is equal to the predetermined value TM.
It is within LLC # (step 32 in FIG. 7). If the conditions are met, TML is not immediately entered for feedback correction.
This is a delay process because the feedback correction is started after waiting the time of LC #. The delay processing is performed because Lljd as the stability signal is the filter processing output, so that the output is not stable immediately even if it is affected by disturbance, and the rotation fluctuation caused by gear change etc. This is because it is better to perform delay processing in order to perform stable feedback correction because it does not disappear instantaneously due to the influence of the vibration system.

Further, the predetermined value TMLLC # is commonly used at the time of transition, switching of auxiliary equipment load, and sudden change.
If a time of about 3 seconds is set, it is possible to cover the rotation fluctuation section at the time of transition of the auxiliary machine load at the time of transition or idling or at the time of sudden change.

When all of the above conditions <1> to <10> are not satisfied, the feedback correction prohibition flag is set to "0" and the feedback correction is started (Fig. 7).
Step 34).

[3] Calculation of Stabilized Fuel-Air Ratio Correction Coefficient In FIG. 9, the stability signal (digital filter processing output Lljd) is sampled every 180 degrees and the number of samples is counted (step 4 in FIG. 9).
1).

A predetermined short sample number S and long sample number L (L> S) to be compared with this count value are obtained (step 42 in FIG. 9). The values of S and L are determined in consideration of detection accuracy (more is better) and control accuracy (less is faster). For example, it is obtained from the engine speed Ne by referring to a table having the contents of FIG.

When the number of S samples is the same, the value obtained by dividing the sum of the sample data by S (that is, the average value) is the first.
If (sample data total / S) ≧ Slh, it is determined that the combustion stability has exceeded the allowable level, and the stabilized fuel-air ratio correction coefficient Lldml as the feedback correction amount is determined. Lldml = Lldml _n-1 + DLLH # (5) where Lldml _n-1 ; Lldml DLLH # one time before; high-speed update amount is updated (steps 44, 45, 46 in FIG. 9).

Even when the number of L samples is uniform, the second slice level Sll (Sll <Slh) is subtracted from the value obtained by dividing the total of the sample data by L, and FIG. 11 is obtained from the subtracted value. The low-speed update amount Dlldml is obtained by referring to the table, and using this value, Lldml = Lldml _n−1 + Dlldml (6) where Lldml _n−1 ; The correction coefficient Lldml is updated (steps 47, 48, 49, 50 in FIG. 9).

The high-speed update amount DLLH # in equation (5) is a positive constant value, but the low-speed update amount Dlldml is as shown in FIG.
As shown in (sample data total / L-Sll)
Is large in the positive region according to (total sample data / L-Sll), and (total sample data / L-Sll)
In the negative region, the negative value is increased according to | total sample data / L-Sll |.

In this way, the stabilized fuel-air ratio correction coefficient Lldml is updated in two steps depending on the number of S samples and the number of L samples. When the slice level Slh, which is a large value, is exceeded in a small number of times, the large update amount DLL for the time being
When H # is used, the value of Lldml is changed to the increasing side in a responsive manner, and when the slice level Sll, which is smaller than Slh, is exceeded at the stage where the number of sample data is large, the update amount according to the exceeded amount is used. This is for changing the value of Lldml with high accuracy.

The stabilized fuel-air ratio correction coefficient Lldml eventually changes the air-fuel ratio during warm-up.
In (1), if the update amount Dlldml is given even in the range where (total sample data / L-Sll) is small, torque fluctuation occurs due to change in air-fuel ratio. In order to prevent this,
In 1 the dead zone (total sample data / L-Sl
Dll when the value of l) is in a predetermined range around 0
The area (dml = 0) is provided.

Finally, the stabilized fuel-air ratio correction coefficient Lldml
When is less than the minimum value of 0, set Lldml = 0,
When Lldml becomes the maximum value LLDMMX # or more,
Lldml = LLDMMX # (step 5 in FIG. 9)
1).

[4] Calculation of Slice Level for Stability Judgment The above two slice levels Slh and Sll used for judging whether or not the stability signal is within the allowable level are not constant values and are shown in FIG. Thus, it is calculated with a variable value. When idling or when the gear position is not in neutral, the rotation speed Ne and the cylinder air amount equivalent pulse width Av
Referring to the map having the content shown in FIG. 13 using tp, and at the time of idling or neutral, the rotation speed Ne
Then, the slice levels Sll and Slh are obtained by referring to the table having the contents of FIG. 14 (steps 61 and 62, steps 61 and 63 of FIG. 12).

As shown in FIG. 13, the slice level Sl used during idling or during running other than neutral
I and Slh were also assigned according to the load of the engine because it was experimentally found to be affected by the load. This is probably because the spring constant of engine mounting changes with load. Note that FIG. 13 shows Sll
And Slh show common characteristics, and it goes without saying that separate maps are actually prepared for Sll and Slh.

The reason why the driving condition is divided into the idling or neutral driving condition and the other running condition is that the influence on the stability is different. At idle or in neutral, only a small mass of the transmission is connected to the engine, which causes large fluctuations in rotation, while during other driving, the vehicle mass is connected to the engine, so combustion does not occur. This is because the rotation fluctuation is relatively small even if it fluctuates.

[5] Correction of cooling water temperature Feedback correction amount (stabilized fuel-air ratio correction coefficient Lldm
The water temperature correction temperature Twl is calculated from l) as follows: Twl = Tw-Lldml (7) where Tw is the cooling water temperature (step 71 in FIG. 15).

According to the equation (7), Twl becomes smaller as it becomes harder to volatilize than general gasoline. This takes advantage of the fact that the difference in volatility of fuels is almost the same as the difference in temperature. That is, the fuel-air ratio correction coefficient Lldml corresponding to the difference in volatility from general gasoline is set to (7)
It is converted into the temperature correction amount by the formula.

[6] Warm-up increase The values for controlling the air-fuel ratio during warm-up include the water temperature increase correction coefficient Ktw and the after-start increase correction coefficient Kas, which are well known. For example, Ktw = Ktw0 * Ktwn (8) where Ktw0: basic value of correction coefficient Ktwn: rotation correction rate, water temperature increase correction coefficient Ktw, and Kas = Kas0 * Kasn * Rtime (9) where Kas0 A basic value of the correction coefficient Kasn; a rotation correction rate Rtime; an attenuation rate is used to calculate the increase correction coefficient Kas after starting (FIG. 1).
6 steps 94, 98).

The only difference from the prior art is that the water temperature correction temperature Twl of the equation (7) is used in place of the cooling water temperature Tw.
Therefore, the basic values Ktw0 and Kas0 are obtained from the water temperature correction temperature Twl by referring to the table having the contents shown in FIG. 18 (steps 92 and 95 in FIG. 16). The table having the content of FIG. 18 is obtained by simply replacing the variable name in the conventional table prepared for general gasoline with Tw instead of Twl, and the data value remains unchanged.

Although the initial value (determined by Kas0 and Kasn) is decreased more slowly at low temperature than at high temperature by the attenuation rate Rtime of the equation (9), this attenuation rate Rti
Also for me, it is determined from the water temperature correction temperature Twl and the time after startup by referring to the table having the content of FIG. 20 (see FIG. 1).
Step 6 of 6).

The rotation correction factor Ktwn of the equations (8) and (9)
And Kasn are obtained by referring to the table having the contents shown in FIG. 19 (steps 93 and 96 in FIG. 16).

[7] Target fuel-air ratio Tfbya This is known Tfbya = Kmr + Ktw + Kas (10) where Kmr is the target fuel-air ratio map value (step 100 in FIG. 16).

The fuel-air ratio is used because the fuel control is performed with the aim of the target air-fuel ratio, and the fuel supply amount is finally obtained from the detected air flow rate.
This is because the fuel-air ratio is easier to handle than the air-fuel ratio because the relationship of (fuel-air ratio) = (fuel supply amount) is established.

The target fuel-air ratio map value Kmr of the equation (10) is obtained from the rotational speed Ne and the load signal with reference to the map having the contents shown in FIG. 17 (step 91 in FIG. 16).

From equation (10), during warm-up immediately after cold start,
The target fuel-air ratio map value Kmr is 1.0 (that is, equivalent to the theoretical air-fuel ratio), and the air-fuel ratio during warm-up shifts to the rich side of the theoretical air-fuel ratio due to the warm-up increase (Kmr and Ktw). is there.

It should be noted that the O ₂ sensor 12 was sufficiently activated, the post-starting time had passed to such an extent that there was no problem in drivability even if there was no increase in the post-starting amount, and the water temperature Tw was above a predetermined value. When all are satisfied, the feedback correction of the air-fuel ratio based on the O ₂ sensor 12 is started. Under this air-fuel ratio feedback correction condition, Tfbya = 1.0 (steps 99 and 101 in FIG. 16), and the three-way catalyst 6 is utilized to the maximum. In the high load range, the air-fuel ratio feedback correction prohibition condition (clamping condition) becomes again, and as shown in FIG. 17, the target fuel-air ratio map value Kmr is made larger than 1.0 (the air-fuel ratio is shifted to the rich side). Meets output requirements.

[8] Calculation of Fuel Injection Pulse Width The fuel injection pulse width Ti output to each injector 4 is Ti = (Avtp + Kathos) * Tfbya * (α + αm) + Ts (11) where Avtp; cylinder air amount equivalent pulse width Kathos; wall flow correction amount Tfbya; target fuel-air ratio α; air-fuel ratio feedback correction coefficient αm; air-fuel ratio learning correction coefficient Ts; invalid pulse width (step 74 in FIG. 15).

The cylinder air amount equivalent pulse width Avtp of the equation (11) is Avtp = Tp * Fload + Avtp _n-1 * (1-Fload) (12) where Tp; basic injection pulse width Avtp _n-1 ; Avtp Fload; value obtained by defining the basic injection pulse width Tp by the formula of weighted average coefficient
p is the intake air amount Qs obtained by A / D converting the air flow meter output and then linearizing it. Tp = (Qs / Ne) * K # * Ktrm (13) where K # is a constant that determines the basic air-fuel ratio. Ktrm is a value calculated by the formula of a constant determined from the flow rate characteristic of the injector (step 72 in FIG. 15).
The expressions (12) and (13) are also known.

The wall flow correction amount Kathos of the equation (11) is
Equilibrium deposition amount Mf for each operating condition is aimed at correcting the low-frequency component of the wall flow (the wall flow that changes relatively slowly).
The value h is stored, and the change in the equilibrium adhesion amount due to the transient is added as a total correction amount to the cylinder air amount equivalent pulse width Avtp (subtracted during deceleration) at a predetermined ratio for each fuel injection. It is known. For example, when accelerating, the injection amount must be increased, but no matter how good the atomization characteristics of the injector, a part of the fuel adheres to the intake manifold wall and flows in the liquid state along the intake pipe wall. Flow is wall flow), flowing into the cylinder at a slower rate than the fuel entrained in the air. That is, since the air-fuel mixture drawn into the cylinder is temporarily thinned by the wall-flow fuel, the wall-flow correction amount Kathos is increased at the time of acceleration in order to prevent the temporary lean mixture. On the contrary, during deceleration when the manifold pressure suddenly becomes a high negative pressure, the fuel adhering to the manifold wall is vaporized all at once,
The air-fuel mixture becomes temporarily too rich, and CO and HC increase. Therefore, during deceleration, the vaporized wall flow is reduced.

Under a constant fuel cut condition such as during deceleration or high rotation, the invalid pulse width Ts is stored in place of Ti in equation (11) (otherwise, Ti is stored in the output register ( By performing steps 78 and 79 and steps 78 and 80 in FIG. 15, the injection timing is prepared.

[9] Injection amount at start-up The use of heavy gasoline greatly affects drivability even during cold start-up. This is because the fuel injection amount required at the time of cold start also greatly differs due to the difference in the volatility of the fuel.

Therefore, the feedback correction amount (Lldml) corresponding to the detected value of the fuel volatility is reflected in the starting injection amount.

[9-1] Battery backup of correction amount The feedback correction of the stability is completed by starting the air-fuel ratio feedback correction using the O ₂ sensor. The ratio correction coefficient Lldml) is held, and the held value is backed up by the battery after the engine is stopped.

[9-2] Calculation of injection pulse width at start-up The basic calculation method is the same as the above-mentioned post-start-up increase correction coefficient Kas except that the variable names are different. However, the time correction rate K
As for cs, as shown in FIG. 24, the increase correction coefficient Ka after starting is
It is slightly different from the case of s (the difference is that when the start switch is turned on and the time of the constant value TKCS1 # has passed or when the start switch ST / SW is turned off, the decrease characteristic is immediately entered).

In FIG. 21, the starting injection pulse width Tst
Is Tst = Tst0 * Csn * Kcs (14) where Tst0 is the basic value of the injection pulse width Csn is the rotation correction rate Kcs is the time correction rate (step 114 in FIG. 21), but the basic value of the injection pulse width Regarding Tst0, the water temperature correction temperature Twl at the time of starting
It is determined by referring to the table having the contents shown in FIG. 22 (step 111 in FIG. 21) from (the same variable name is used as the method of calculating the water temperature correction temperature Twl). Also in this table, the parameter of the conventional table is simply changed from Tw to Twl, and the data remains the same.

Whether it is a start or not (14)
The starting injection pulse width Tst is calculated from the equation and is set as Ti (steps 75 and 76 in FIG. 15).

Thus, the feedback correction amount (Lldml) obtained for the fuel used during the previous operation
Is retained by the battery backup even after the engine is stopped, and if the injection amount at startup is calculated based on this retained feedback correction amount, as long as the same fuel is continuously used this time, that amount is maintained even at cold start. The optimum injection amount for the used fuel is supplied. For example, if heavy gasoline was used during the previous operation, when heavy gasoline is used again this time, more fuel will be supplied than for regular gasoline. The operability at the cold start is improved even when the is used.

Further, since the starting injection amount can be calculated by directly using the conventional table or map (the table of characteristics shown in FIG. 22 is one in which the variable names are simply replaced), the table and the map can be calculated. There is no significant increase in man-hours for creation.

Here, the operation of this example will be described with reference to FIG. 26, which is when the air conditioner switch is switched.

At the time of switching the air conditioner switch, a rotational fluctuation unrelated to combustion instability occurs. Therefore, at the time of this switching, the stabilized fuel-air ratio correction is performed so that the stability signal (digital filter processing output Lljd) falls within the allowable level. Coefficient Ll
When dml is updated, the stabilized fuel-air ratio correction coefficient Lldm
l becomes large as indicated by the broken line, and the air-fuel ratio is erroneously controlled to the rich side (inviting deterioration of fuel consumption and increase of CO and HC).

On the other hand, in this example, when the air conditioner switch is switched, the stabilized fuel-air ratio correction coefficient Lldml
Is prohibited from being updated, as shown by the solid line, the stabilized fuel-air ratio correction coefficient Ll is set immediately after switching the air conditioner switch.
Since dml does not change, the air-fuel ratio will not be erroneously controlled to the rich side. Even if the rotation fluctuation occurs due to the switching of the air conditioner switch, the fuel consumption is deteriorated and C
The increase of O and HC can be prevented.

Further, if the update is prohibited for a predetermined period (see the section indicated by the arrow) from the time of switching the air conditioner switch, it is possible to reliably prevent erroneous control of the air-fuel ratio to the rich side. Since the rotation fluctuation accompanying the switching of the air conditioner switch continues for a while immediately after the switch switching, the predetermined period is set in accordance with this period.

Similarly, even if the update of the stabilizing fuel-air ratio correction coefficient is prohibited when the power steering switch or the electric load switch where the auxiliary load changes abruptly, the air-fuel ratio is erroneously controlled to the rich side. Fuel efficiency and C
It is possible to prevent an increase in O and HC.

In the embodiment, the updating of the stabilized fuel-air ratio correction coefficient is prohibited, but it goes without saying that the same effect can be obtained by making the updating amount extremely small.

The above-described stability control can be performed in the lean burn engine even in the lean air-fuel ratio range. The feedback correction amount is updated so that the stability signal stays within the allowable level in the lean air-fuel ratio region, and the map value of the target air-fuel ratio in the lean air-fuel ratio region is corrected with the air-fuel ratio correction amount obtained based on this feedback correction amount. To do.

Also in this case, by prohibiting the update of the feedback correction amount when the load of the auxiliary machine suddenly changes, the operation is temporarily increased by NOx due to the erroneous control of the air-fuel ratio in the rich direction and the torque is increased (then it is decreased). It is possible to prevent deterioration of sex.

[0105]

According to the first aspect of the present invention, the means for calculating the basic control amount of the engine control factor from the engine operating condition signal, the means for calculating the combustion stability from the engine rotation fluctuation, and the stability Means for updating the feedback correction amount so that the detected value falls within an allowable level, means for calculating the correction amount for the basic control amount based on this feedback correction amount, and the basic control amount is corrected with this correction amount. Means for calculating the control amount of the engine control factor, means for controlling the engine control factor with this control amount, means for judging whether or not there is a sudden change in the auxiliary machine load, and the auxiliary machine load based on this judgment result. Since the means for prohibiting the update of the feedback correction amount at the time of sudden change is provided, erroneous control is not performed even if the rotation fluctuation may occur due to the sudden change of the auxiliary machine load.

According to the second aspect of the present invention, the prohibition of the update of the feedback correction amount is from the time of the sudden change of the auxiliary equipment load to the time after a predetermined period, so that the erroneous control can be reliably prevented.

[Brief description of drawings]

FIG. 1 is a diagram corresponding to a claim of the first invention.

FIG. 2 is a control system diagram of an embodiment.

FIG. 3 is a flow chart of a 180 degree job.

FIG. 4 is a flowchart for explaining calculation of fluctuations.

FIG. 5 is a waveform diagram showing the relationship between combustion pressure, rotation speed, and reference signal in the case of a 4-cylinder engine.

FIG. 6 is a waveform diagram for explaining a measurement section.

FIG. 7 is a flowchart for explaining determination of stability feedback correction conditions.

FIG. 8 is a diagram showing a region where stability feedback correction is performed.

FIG. 9 is a flowchart for explaining calculation of a stabilized fuel-air ratio correction coefficient Lldml.

FIG. 10 is a characteristic diagram showing table contents of predetermined sample numbers S and L.

FIG. 11: Update amount D of stabilized fuel-air ratio correction coefficient Lldml
It is a characteristic view which shows the table content of lldml.

FIG. 12 is a flowchart of a background job.

FIG. 13 is a characteristic diagram showing map contents of two slice levels Sll and Slh.

FIG. 14 is a characteristic diagram showing the table contents of two slice levels Sll and Slh.

FIG. 15 is a flowchart of a 10 msec job.

FIG. 16 is a flowchart for explaining calculation of a target fuel-air ratio Tbya.

FIG. 17 is a characteristic diagram showing map contents of a target fuel-air ratio map value Kmr.

FIG. 18 is a characteristic diagram showing table contents of basic values Ktw0 and Kas0 of correction coefficients.

FIG. 19 is a characteristic diagram showing table contents of rotation correction factors Ktwn and Kasn.

FIG. 20 is a characteristic diagram showing the table contents of the attenuation rate Rtime.

FIG. 21 is a flow chart for explaining calculation of a starting injection pulse width Tst.

FIG. 22 is a characteristic diagram showing the table contents of the basic value Tst0 of the injection pulse width.

FIG. 23 is a characteristic diagram showing table contents of a rotation correction rate Csn.

FIG. 24 is a characteristic diagram showing the table contents of the time correction rate Kcs.

FIG. 25 is an electric circuit diagram of an auxiliary load.

FIG. 26 is a waveform diagram for explaining an operation at the time of switching the air conditioner switch.

[Explanation of symbols]

 4 Injector (fuel supply device) 7 Air flow meter 9 Idle switch 10 Crank angle sensor 11 Water temperature sensor 21 Control unit 32 Air conditioner switch 34 Power steering ring switch 37 Heater fan switch 40 Light switch 43 Rear defogger switch 51 Basic control amount calculation means 52 Combustion stabilization Degree calculation means 53 feedback correction amount update means 54 correction amount calculation means 55 control amount calculation means 56 control factor control means 57 auxiliary equipment load sudden change judgment means 58 update prohibition means

Claims (2)

[Claims] 1. A means for calculating a basic control amount of an engine control factor from an engine operating condition signal, a means for calculating a combustion stability from an engine speed fluctuation, and a detected value of the stability falling within an allowable level. Means for updating the feedback correction amount, means for calculating the correction amount of the basic control amount based on the feedback correction amount, and the control amount of the engine control factor for correcting the basic control amount with this correction amount. A means for calculating the engine control factor with this control amount, a means for determining whether or not there is a sudden change in the auxiliary machine load, and a determination result of this feedback correction amount when the auxiliary machine load changes suddenly. An engine stability control device comprising means for prohibiting updating. 2. The engine stability control device according to claim 1, wherein the prohibition of updating the feedback correction amount is from a time when the auxiliary load suddenly changes to a time after a predetermined period.